title: Mapping afforestation and deforestation from 1974 to 2012 using Landsat time-series stacks in Yulin District, a key region of the Three-North Shelter region, China.
abstract: The Three-North Shelter Forest Program is the largest afforestation reconstruction project in the world. Remote sensing is a crucial tool to map land use and land cover change, but it is still challenging to accurately quantify the change in forest extent from time-series satellite images. In this paper, 30 Landsat MSS/TM/ETM+ epochs from 1974 to 2012 were collected, and the high-quality ground surface reflectance (GSR) time-series images were processed by integrating the 6S atmosphere transfer model and a relative reflectance normalization algorithm. Subsequently, we developed a vegetation change tracking method to reconstruct the forest change history (afforestation and deforestation) from the time-series Landsat GSR images based on the integrated forest z-score (IFZ) model by Huang et al. (2009a), which was improved by multi-phenological IFZ models and the smoothing processing of IFZ data for afforestation mapping. The mapping result showed a large increase in the extent of forest, from 380,394 ha (14.8% of total district area) in 1974 to 1,128,380 ha (43.9%) in 2010. Finally, the land cover and forest change map was validated with an overall accuracy of 89.1% and a kappa coefficient of 0.858. The forest change time was also successfully retrieved, with 22.2% and 86.5% of the change pixels attributed to the correct epoch and within three epochs, respectively. The results confirmed a great achievement of the ecological revegetation projects in Yulin district over the last 40 years and also illustrated the potential of the time-series of Landsat images for detecting forest changes and estimating tree age for the artificial forest in a semi-arid zone strongly influenced by human activities.
authors.affiliation: Key Laboratory of Digital Earth Science, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing, 100094, China, liuliangyun@sina.com.
authors.forename: Liangyun
authors.initials: L
authors.lastname: Liu
authors.forename: Huan
authors.initials: H
authors.lastname: Tang
authors.forename: Peter
authors.initials: P
authors.lastname: Caccetta
authors.forename: Eric A
authors.initials: EA
authors.lastname: Lehmann
authors.forename: Yong
authors.initials: Y
authors.lastname: Hu
authors.forename: Xiaoliang
authors.initials: X
authors.lastname: Wu
mesh_terms: D001272:Atmosphere; D002681:China; D003247:Conservation of Natural Resources / Q000639:trends; D004784:Environmental Monitoring / Q000379:methods*; D016468:Forestry; D063809:Satellite Imagery; D014197:Trees / Q000254:growth & development*